A scanning probe microscope (SPM) is known as a measuring technology of fine three-dimensional shapes. This is a technology that scans a sample while a probe whose tip is pointed is controlled and contact force is kept at an extremely small value, and has widely been employed as a technology capable of measuring fine three-dimensional shapes in an atomic order. Various improvements have been made in the past to solve the problem inherent to the scanning probe microscope in that it is difficult to increase a speed for physically scanning the sample.
For example, JP-A-10-142240 and JP-A-2000-162115 disclose a technology for correcting shape data from both deflection signal of a probe and driving signal of a sample to simultaneously satisfy high speed and resolution. In order to bring at a high speed the probe close to the sample, JP-A-6-74754 discloses a technology that brings at a high speed a probe close to a sample by utilizing the fact that when the probe is allowed to approach the sample while being oscillated, the probe can be constituted in such a manner that amplitude of the probe decreases from a position spaced apart by about 5 micro-meter due to acoustic interaction. However, the technologies described above involve the problem that only a scanning probe microscope apparatus having the construction for oscillating the probe can be used and the problem that because proximity cannot be detected unless the probe approaches the sample at about several micro-meters, another sensor becomes necessary to bring at a high speed the probe to the distance of several micro-meters.
On the other hand, existing fine pattern formation processes of LSI conduct dimensional management by using CD-SEM (measuring SEM, CD: Critical Dimension) but the following problems to be solved exist with miniaturization of patterns.    (1) Problem of measurement accuracy:
Gate width of 90 nm node LSI, which is expected to become predominant in 2003, is 80 mm, and required measurement accuracy is 1.6 mm when allowable dispersion is 10% and measurement accuracy is its 20%.    (2) Requirement of profile measurement:
Needs for APC (Advanced Process Control) have increased for high precision control of line width. For this purpose, a measurement technology of not only the pattern line with but also a sectional shape exerting great influences on electrical characteristics is necessary.    (3) Problem of measurement objects:
Measurement needs for materials having low electron beam resistance such as DUV (deep UV) resists, low-k (low dielectric constant) film materials, etc, have increased.    (4) The necessity for APC (Advanced Process Control) has increased for high precision control of the line width and for this purpose, a measurement technology not only of the pattern line width but also a sectional shape exerting great influences on electrical characteristics is necessary.    (5) Similar needs such as similar measurement accuracy, the necessity of profile measurement and measurement of a resist pattern for preparing a master are assumed for the measurement of pits of a high density optical disk memory of the next generation.
Existing CD-SEM cannot cope with the problems described above. Therefore, a scanning probe microscope technology is believed promising. It is a scanning probe microscope technology capable of increasing the probe approach speed described above, less damaging a soft and brittle material and capable of acquiring information of surface materials that becomes necessary in this case.
In contrast, JP-A-11-352135 discloses a method for reducing damage of a soft and brittle material by oscillating a sample or a probe at constant amplitude and conducting scanning while the probe is allowed to periodically impinge against the sample.
Further, JP-A-2001-33373 discloses a scanning method which applies servo of a probe at only sporadic measurement points to measure a height and moves the probe towards the next measurement point while the probe is pulled up. According to this method, the number of times of contact is small and damage to the soft and brittle material and the probe is less. Because the probe is not dragged, there is the advantage that the shape at a step portion can be measured with fidelity. From the aspect of the higher speed, however, high speed measurement cannot be made because retraction and approach of the probe is repeated for each measurement point.
However, when the atomic force microscope (AFM) is used for CD/sectional profile measurement in the semiconductor production lines, there are many problems to be solved such as through-put, specification and positioning of the measurement area, distortion of the measurement image resulting from scanning accuracy of an XY stage or variance of the probe shape and probe wear, and so forth.
As for positioning of the measurement area among the problems when the atomic force microscope (AFM) is used for the CD measurement, a method that assembles an optical microscope having high magnification in AFM has been used at present and positioning by the optical microscope image is conducted (refer to JP-A-2-28113 (Summary on page 1, etc), for example).
As a method of sample observation other than the optical microscope, a composite apparatus of a scanning electron microscope and an atomic force microscope (AFM) has been considered (refer to JP-A10-223170 (Summary on page 1, etc), for example).
Further, the method disclosed in JP-A-2-28113 described above involves the problem that accurate positioning of the measurement area becomes impossible in future because resolution of patterns by using the optical microscope becomes more difficult with further miniaturization of the patterns.
In the technology described in JP-A-10-223170 described above, the apparatus becomes large in scale and damage to samples having low electron beam resistance is feared. Another problem is that the operation of monitoring the probe shape and the wear amount of the probe due to the measurement and judging the probe exchange timing or eliminating the influences on the measurement profile distortion due to the probe shape difference and the probe wear becomes an unavoidable operation for conducting highly accurately the CD measurement.
As explained above, the prior art technologies have the problems how to simultaneously satisfy the measurement not damaging the sample and the high speed measurement.